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Use the following steps to complete the wiring of the breadboard

  • Select your circuit. If this is your first time, choose the SR NAND or SR NOR.
  • Operate the switches in the circuit simulator. Read the description of the circuit if you need additional information.
  • Using the schematic, wire up the circuit in the breadboard simulator. When a wire end is placed in a socket of the breadboard that corresponds to a node on the schematic, the respective node of the schematic will turn red.
  • If a correct connection is made, the wire ends will snap into the socket.
  • Note that all the VCC (red wire) and GND (black wire) connections are already done.
  • When all the nodes are wired up, a red LED will light up near the VCC/GND terminals.
  • You may now operate the breadboard switches and observe the LED results.
  • When you wire up the circuit using a real digital trainer, do remember to wire the VCC and GND wires and power up the digital trainer.
  • You must login using your facebook account to save or restore the breadboard connections.
  • Click to close any of the panes (breadboard/schematic/description/help) and click on the corresponding menu item to open it.

If you are unfamiliar with the breadboard, there are many resources available online that explains how to they work.

Truncated Ripple Counter

The natural count sequence is to run through all possible combinations of the bit patterns before repeating itself. External logic is used to cause the counter to terminate at a specific count. A decade counter counts from 0 to 9, thus making it suitable for human interface. A MOD 12 truncated ripple counter is used for clocks.

  • The circuit is a MOD 3 truncated ripple counter. It counts up from 00, 01, 10, and resets to 00.
  • The D flip flops are connected to toggle. This flip flop has a rising edge clock.
  • Click on CLK (SW7) switch and observe the changes in the outputs of the flip flops. The CLK switch is a momentary switch
  • This counter counts up from 00. Normally the output of the NAND gate is 1. When the count reaches 11 (decimal 3), the NAND gate outputs a 0 which clears the flip flops to 00. In real operation, this state is only momentary (a glitch), time enough to clear the flip flops.
  • Without the NAND gate, the counter will reach the full count and is a MOD 4 counter (22)